What
does preparedness for an earthquake actually mean? Can there be an effective
earthquake warning system? Before we look into the questions let us first
briefly see what is an earthquake and how does it come about?
According
to definition, earthquakes are the result of shifting or movement of earth’s
tectonic plates. Earthquakes occur when the frictional stress of gliding plate
boundaries builds and causes rupture at a fault line. As a result, elastic
strain energy is released and waves radiate, shaking the ground.
As
we know, major earthquakes affect large areas of population either by
generating tsunamis or leveling the entire cities. Comparatively speaking,
minor earthquakes can also be induced or caused by human activities like
extraction of minerals from the earth and the collapse of large buildings.
Scientists
can predict where major earthquakes might happen in a general sense, but
research does not yet allow forecasts for specific locations or accurate
predictions of timing.
Approximately,
two-thirds of the total area of Pakistan is on fault lines, putting the lives
and property of more than 170 million people at risk. Now and then, experts
have expressed concerns that neglecting the fault lines while making big
structures in cities might be the cause of massive destruction.
Pakistan
has been hit by some forty earthquakes to this day, some of them deadly.
Recently, Pakistan was jolted by an intense earthquake of 7.7 magnitude. The
epicenter of the earthquake was 69km north of Awaran district in Quetta and
some 270km north of Karachi. The shocks were also felt in Turbat, Panjgur,
Chaghai, Khuzdar, Gwadar, Quetta, Hub, Kharan, Jhal Magsi, Qalat, Sibi,
Mastung, and Jafferabad, and even in Karachi.
Four
major tectonic plates — Arabia, Eurasia, India, and Africa — and one smaller
tectonic block — Anatolia — are the cause for tectonic activities in the Middle
East and the adjacent regions.
In
geological terms, the Aawran earthquake occurred due to oblique north-south to
northeast-southwest strike-slip type motion at shallow crustal depths that is
primarily accommodated on the Chaman faultline, with the earthquake potentially
occurring on one of the southern-most strands of this fault system.
The
Chaman faultline runs along Pakistan’s western frontier with Afghanistan from
Kalat, in the northern Makran range, past Quetta and then on to Kabul,
Afghanistan. A faultline also runs along the Makran coast and is believed to be
of the same nature as the west coast faultline along the coast of Maharashtra,
India.
We
cannot totally escape from an earthquake but we can be a survivor if given a 60
seconds head start before an impending earthquake due to an early-warning
system. How is it possible to issue a warning of the phenomenon that cannot
even be predicted?
The
statement of seismologist, Richard Allen, director of the Seismological Laboratory
at the University of California, Berkeley, aptly resolves this paradox.
Generally, when people talk about prediction, they’re talking about when an
earthquake will occur — when rocks in a fault slip past each other. Most
seismologists say we won’t be able to predict this for the foreseeable future.
We’re predicting the shaking that comes from when the earthquake ruptures. So,
basically, an earthquake has already started.
People
think of an earthquake as being an instantaneous occurrence. It’s not. The
energy that radiates out from an earthquake is what causes the shaking that
people feel. P waves come first and S waves come next, as they carry most of
the energy so they do most of the damage. The intensity of the shaking that’s
carried by the S waves can be estimated, and that’s the basis for an early
warning. Basically, the warning provides an advantage of sixty seconds which,
in turn, also depends on the distance from the epicenter.
Earthquake
early-warning system is designed to detect the first strong pulse coming from
an earthquake, which carries information about its size. This shockwave travels
faster than the slower waves that do most of the shaking damage during an
earthquake. The farther you are from an earthquake’s epicenter, the more warning
you get. Therefore, the governments in some of the earthquake-prone countries,
like Japan, Mexico, and the State of California, institute early warning
systems to alert the public to expect potentially hazardous shaking.
In
2007, Japan launched a comprehensive nationwide online earthquake early-warning
system. It is considered as one of the most advanced systems as yet. It detects
tremors, calculates an earthquake’s epicenter and sends out brief warnings from
its 1,000-plus seismographs scattered throughout the country via mobile phones,
radio, TV, and sirens. Area Mail Disaster Information Service disseminates
earthquake early warnings issued by Japan Meteorological Agency.
The
subscribers of the service receive the information via mobile phones either in
the form of pop-up display or special emergency tone. In California, the
scientists are in the early stages of developing the techniques and framework
of earthquake early-warning system. They are following the lead of Japan in
developing their warning system.
Although
the early warning systems can only give warnings from seconds to one or two
minutes before the powerful S-waves hit and shaking gets serious, it can mean
the difference between life and death. It can be just enough time to take
cover, drive a car to the side of the road, step back from getting on an
elevator or stop medical surgery, turn off gas burners, or duck preparedness,
move away from windows, etc, to reduce the risk of injury and minimize damage.
Experts
say most of the major cities of Pakistan are located on the faultline, which
also crosses the centre of Margalla Hills. Therefore, Pakistan Meteorological
Department (PMD) should work on developing an effective earthquake warning
system. Moreover, PMD should enhance the potentiality of the existing National
Seismic and Tsunami Monitoring System that is responsible for disseminating
earthquake information.
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